Research brief: Does climate change cause longer and more frequent marine heatwaves?

Marine heatwaves are becoming longer and more frequent, and they are having major impacts on marine ecosystems. After each event we often ask the question: did climate change cause it?

Here we use a suite of global climate models to address this question for two of the most extreme marine heatwaves from 2016. Across northern Australian a spell of warm ocean temperatures caused catastrophic and extensive damage to the Great Barrier Reef. And south of Alaska, extreme sea-surface temperatures rose up to 2 degrees above average across the Gulf of Alaska and the Bering Sea, persisting for months. Both events were unprecedented in the historical record.

We examined the likelihood of these events in global climate models simulations, with and without anthropogenic influences, and found that these events were up to fifty times more likely due to anthropogenic climate change.